U.S. Pat. Nos. 4,027,660; 4,091,659; 4,137,755; 4,209,226; 4,558,947; 4,683,579; 5,132,087; 5,888,184; and 6,441,890 describe methods and apparatus for hematological analysis using a capillary tube and a space occupying insert that floats on the centrifuged red blood cells thereby expanding the surrounding buffy coat and permitting the measurement and quantization of the blood's layers. This method permits the determination of a compete blood count (CBC) consisting of hematocrit, a hemoglobin determination, a total white blood cell count with the latter presented as a total and percent granulocytes and total and percent lymphocytes plus monocytes, as well as a platelet count and a mean red cell hemoglobin concentration. It is widely used through the world for performing point of care CBC in human and veterinary medicine. The device, formerly manufactured and sold by Becton Dickinson, Inc. of New Jersey U.S.A. is now manufactured and sold by QBC Diagnostics, Inc., of Pennsylvania, U.S.A. The apparatus is sold under the trademark of QBC® hematology. The capillary tubes are referred to in the industry as “QBC® tubes”.
The QBC® hematology system includes a number of different complex instruments for reading the QBC® tubes, each of which has an illumination system, a power source, an imaging and optical system, a microprocessor, and a display. These devices can cost anywhere from several hundred to many thousands of U.S. dollars. The current versions of both the stand-alone reader and the integral reader-centrifuge (QBC® STAR reader) provide for a linear scan of the tube, either while it is stationary in the case of the stand-alone reader or while the centrifuge is in motion, as is the case with the QBC® STAR reader. In both cases, the linear scan is limited to scanning a single axially extending line scan of the tube, which evaluates only a thin stripe of the area of interest within the tube. Because this method of scanning can only scan a thin stripe of the area of interest at a given time, it is necessary to take multiple axially extending scans taken at different circumferential positions of the tube to determine which of the scans can be used for analytical purposes. By looking at several different scans, each taken at a different circumferential position, it is possible to ascertain whether any particular scan is representative of the sample or if it contains an unrepresentative anomaly. Also, because of the narrow scan, the mechanical and optical alignment of the instrument must be held to a very high tolerance, which also increases the cost of the device.
This is particularly true in the case of the QBC® STAR reader, because the QBC® tube is read while the centrifuge is in motion, necessitating an elaborate timing system to ensure that illumination occurs exactly when the tube is in position under the linear scanning device (e.g., CCD scanner). Another, related problem is the need to provide elaborate vibration damping so that the relative tube and reader position be maintained during this process.
These considerations cause the analysis tube readers to have a relatively high price, which limits the market size for the QBC® hematology system because health care providers are reluctant and/or unable to make the requisite equipment investment when the equipment is only used for a few tests per day. In those instances when the point of care giver does not have the analysis equipment, the patient is subjected to the significant inconvenience, harm and expense of having to go to a private laboratory and having to wait often several days to get the result. The lack of an analysis device also makes the physician's job more difficult by precluding immediate results at the point of care. Additionally, regulatory requirements of the United States require that the providers of the test be subject to regulatory supervision under the CLIA (Clinical Laboratory Improvement Act) laws.
What is needed, therefore, is a simple, inexpensive, robust method for reading the centrifuged blood sample at the point of care with immediate availability of results while the health care providers are still with the patient. In addition, a method and device are needed that can provide accuracy results and methodological adherence to proper analytic techniques, as well as quality control measures, particularly those that will permit CLIA waiving, which is subject to less burdensome regulations.